Ib-substituted yohimbone derivatives



United States Patent 3,125,579 Iii-SUBSTITUTED YOHIMBONE DERIVATIVES. AND PROCESS THEREFOR John Shavel, Jr., Mendham, and Harold Zinnes, Denville, NJ., assignors to Warner-Lambert Pharmaceutical Company, Morris Plains, N.J., a corporation of Delaware No Drawing. Filed July 11, 1961, Ser. No. 123,106 7 Claims. (Cl. 260-288) The present invention realtes to new and novel 18 substituted derivatives of yohimbone of the formula OH E 18 u (in-R1 wherein R is phenyl substituted with one or two electron withdrawing groups such as halogen, nitro, trifluoromethyl and the like, and R is hydroxyl or keto. This invention also relates to a method of preparing these compounds and to the pharmaceutically acceptable non-toxic acid addition and quaternary ammonium salts thereof. Useful R substituents include p-chlorophenyl, p-bromophenyl, p-fluorophenyl, p-trifluoromethylphenyl, 3,4-dichlorophenyl, p-nitrophenyl, m-nitrophenyl, o-nitrophenyl, m-chlorophenyl, 2,4 dinitrophenyl, o-bromophenyl and the like.

The compounds of this invention bear the A, B, C, D, and E rings as depicted in the above structural formula and are, generally, alkaloids of the yohimbane series. Depending upon the configuration of the hydrogen atom at the 3-position and the existence of cis or trans fusion of the D and E rings, four different configurations are possible, that is yohimbane, B-epiyohimbane, alloyohimbane and B-epialloyohimbane. The present invention includes within its scope derivatives of these four families of alkaloids bearing substituents at the 17 and 18 positions, respectively.

The compounds of this invention have interesting and significant pharmacological activity and are useful as anti-inflammatory agents. In addition, they are valuable intermediates in the production of other compounds of the yohimbane series. For example, heating the compounds of our invention bearing a keto group at the 17- position results in their dehydration to form compounds bearing a =CHR substituent at the l8-position. Such compounds are described and claimed in the application of John Shavel, Jr., George Bobowski and Maximilian von Strandtmann entitled Yohimbone Derivatives and Process Therefor, Serial No. 123,119, filed concurrently herewith.

' Patented Mar. 17, 1964 We have now found that the reaction of 17-ketoyohimbane alkaloids of the formula either in the pure state or in the state in which they are obtained in the course of synthetic processes, with an aldehyde of the formula R -CHO at a temperature of about 20 C. to 40 C. results in the preparation of those compounds of our invention having the formula wherein R is as described hereinabove.

The reaction is carried out in an inert solvent such as methanol or ethanol in the presence of aqueous alkali, for example sodium hydroxide or potassium hydroxide. Upon completion of the reaction, which normally requires about 5 to about 40 hours, the precipitate, which constitutes the desired product, is purified by crystallization.

The compounds prepared as described above may be converted to compounds of the formula I OH The compounds of this invention may be converted into their pharmaceutically acceptable non-toxic acid addition or quaternary ammonium salts. Useful acid-addition salts are those formed with such acids as maleic, fumaric, benzoic, succinic, methylsulfonic, sulfonic, citric, tartaric, salicyclic, malic, cinnarnic, hydrochloric, hydrobromic, phosphoric and the like. The acid addition salts may be prepared in the conventional manner, for example, by treating a solution or suspension of the free base in an organic solvent with the desired acid, and then recovering the salt which forms by crystallization techniques. The quaternary salts are prepared by heating a solution of the base in a suitable solvent with a reactive alkyl halide such as methyl iodide, ethyl bromide, n-hexyl bromide, benzyl chloride or another reactive ester such as methyl sulfate, ethyl sulfate or methyl p-toluene sulfonate.

For therapeutic use, the new and novel compounds of this invention, either as the free base or in the form of a pharmaceutically acceptable, non-toxic acid addition or quaternary ammonium salt, may be formulated with a conventional pharmaceutical carrier to form tablets, capsules, elixirs, solutions, suspensions, suppositories and the like.

The following examples are included in order further to illustrate the present invention:

EXAMPLE 1 l 8- or-Hydroxy-p-Nitrobenzyl) Yohimbone EXAMPLE 2 Found 18-(wHydroxy-p-Chlorobenzyl) Yohimbone A mixture of 15 g. yohimbone, 25 ml. benzaldehyde, 15 ml. 10% aqueous sodium hydroxide, and 450 ml. methanol is stirred at room temperature for twenty hours and then allowed to stand at room temperature overnight. The crystals which form are recrystallized from acetonitrile to give 12.2 g. of product, which melts at 208-214, resolidifies and melts again at 275280; M1 -96 (pyridine, c.-=0.63). Recrystallization from acetonitrile gives pure 18 (a-hydroxy-p-chlorobenzyl)yohimbone which melts at 229232, resolidifies and remelts at 284289, -94 (pyridine, c.=0.5).

Analysis-Cale: C, 71.79; H, 6.26; N, 6.44; Cl, 8.65. Found: C, 71.84; H, 6.38; N, 6.33; CI, 8.55.

EXAMPLE 3 18-(m-Hydr0xy-3,4-Dichl0r0benzyl) Yohimbone A mixture of 10 g. yohimbone, 15 g. 3,4-dichlorobenzaldehyde, 15 ml. 10% aqueous sodium hydroxide, and 500 ml. methanol is stirred at room temperature for eighteen hours. An additional g. 3,4-dichlorobenzaldehyde are added, the mixture is stirred six hours longer, and then is allowed to stand over-night at room temperature. The crystals which form are filtered off, washed with methanol, and dried in vacuo at 80 for 3 hours. Yield: 14.2 g., M.P. 207209, [M -85 (pyridine, c.=0.88). Recrystallization from acetonitrile gives 18- 4 (a-hydroxy 3,4 dichlorobenzyl)yohimbone, M.P. 2l9 221 dec., (pyridine, c.=0.55).

Analysis.-Calc.: C, 66.52; H, 5.58; N, 5.97; Cl, 15.11. Found: C, 66.47; H, 5.73; N, 6.20; Cl, 15.08.

EXAMPLE 4 18-(a-Hydr0xy-3,4-Dichl0r0benzyl) Yohimbol A mixture of 7 g. 18-(a-hydroxy-3,4-dichlorobenzyl)- yohimbone, 6 g. potassium borohydride, and ml. methanol is stirred at room temperature for two hours, showing that the reaction is complete. The methanol is removed by distillation in vacuo and the residue is triturated with 150 ml. water. The resulting precipitate is filtered off, washed with water, air dried, and recrystallized from methanol. Two recrystallizations yield 3 g. of 18-(a-hydroxy-3,4-dichlorobenzyl)yohimbol as a monomethanolate, M.P. 253-255 dec., [0c] l0l (pyridine, c.=0.63).

Analysis.-Calc.: C, 64.41; H, 6.41; N, 5.56; Cl, 14.09. Found: C, 64.50; H, 6.35; N, 5.68; CI, 13.95.

Throughout the specification, all temperatures are given in degrees centigrade.

It is understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. A member selected from the group consisting of compounds of the formula wherein R is phenyl substituted with one to two members selected from the group consisting of halogen, nitro and trifluoromethyl and R is a member selected from the group consisting of keto and hydroxyl, and the pharmaceutically acceptable non-toxic acid addition and quaternary ammonium salts thereof with a compound selected from the group consisting of methyl iodide, ethyl bromide, n-hexyl bromide, benzyl chloride, methyl sulfate, ethyl sulfate and methyl p-toluene sulfonate.

2. 18-(u-hydroxy-p-nitrobenzyl)yohimbone.

3. 18-(a-hydroxy-p-chlorobenzyl)yohimbone.

4. 18-(zx-hydroxy-3,4-dichlorobenzyl)yohimbone.

5. 18-(a-hydroxy-3,4-dich1orobenzyl)yohimbol.

6. A method of preparing compounds of the formula H-Ri wherein R is phenyl substituted with one to two members selected from the group consisting of halogen, nitro and trifluoromethyl which comprises treating a compound with an aldehyde of the formula R --CI-IO at a temperature of about 20 C. to about 40 C. in an inert solvent in the presence of aqueous alkali.

7. A method according to claim 6 wherein said inert solvent is methanol and said alkali is sodium hydroxide.

6 References Cited in the file of this patent UNITED STATES PATENTS 2,796,420 Weisenborn June 18, 1957 5 FOREIGN PATENTS 1,199,433 France June 22, 1959 OTHER REFERENCES Fieser et al.: Organic Chemistry (1950), pages 116- Theilheimer: Syn. Meth. of Org. Chem, vol. 9 (1955), page 351.

Theilheimer: Syn. Meth. of Org. Chem, vol. 11 (1957), pages 27 and 28.

Theilheimer: Syn. Meth. of Org. Chem, vol. 12 (1958), page 35 (article No. 68).

Wheeler et al.: Chem. Abstracts, vol. 53 (1959), page 7241. 

1. A MEMBER SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF THE FORMULA 